main bearings

[Housel]

I have a mf50 with a gas z134 and I need to replace the main and rod bearings.Will I have to remove the crankshaft to change the main bearings?

 

[vegaome]

Howdy Housel.

I'm not a mechanic but I do tear stuff apart from time to time and sometimes I get it back together. I believe it is possible to remove the bearing caps one at a time. The one half of the bearing will be with the cap and you may be able to roll the other half of the bearing out with the bearing from the cap or some other implement. I have never tore a tractor engine down but have done some truck motors. I always pulled the crank out so I could better evaluate the gernals on the crank. I have heard of people heating a bearing in oil to get it back together.

So I believe it can be done I have just never done it myself. Many folks will advise against it unless you know the crank has never been turned down (which would require an oversized bearing) and the gernals are in good shape. I do understand that sometimes you have to do what you can get by with. Just a word of warning, in the long run it could end up costing more. I try to repairs things the best way I can afford at the time.

I am interested in hearing any sucess stories folks have had doing it this way. I wish you luck and have a good evening. Do keep us posted how it turns out be it good or bad.

v/r

Mike

 

[pjbci]

I have done quite many in frame overhauls this way. Just slightly loosen all your main bearing caps then remove one at a time and roll out the old bearings roll in the new. I use a flexible piece of plastic to push bearings in and out with to prevent marring the crank.

 

[vegaome]

Howdy pjbci,

How do you determine if the crank has never been turned before, do you just use plastigauge?

v/r

Mike

 

[pjbci]

All of em that i have done were either bought new by me or my father or with low enough hours that they had never been rebuilt before. Im on my second inframe overhaul on a 3406 cat truck engune with over 2 million miles on it.
Im not sure but i think the bearings themselves have it stamped on em if they are undersized.

 

[The kid]

I have a mf50 with a gas z134 and I need to replace the main and rod bearings.Will I have to remove the crankshaft to change the main bearings?

Here's my take on this. You say you want to replace both main and rod bearings without dressing the journals. You need to know if they crank has ever been turned or polished. This can be verified with a mic the diameter of the mains, and rod journals. Now how tight is the new bearings going to be. There is a tool called plastigauge where you take a piece of special plastic and place between the bearings and the journals. Torque down the bolts. Now unbolt and measure the width of the plastigauge to determin clearance on each bearing. This will tell you if the bearing is on the money or oversized.

As for the main bearings. How would you replace the block side bearings without removing the crank? Rod bearings could be replaced one at a time without removing the crank. Be sure to take a center punch and mark the rods and caps to identify each cylinder. One to one, two to two an so forth. But the main bearings hold the crank mark them too.. If it where me, I'd have the crank polished regardless. If you have really good compression then your cylinders might be ok. I would hate to tear one down that far and not do a compression check to see it rings and sleeves are needed as well. Main seals are a must at this point. To do what your wanting to do, you'll have to split the tractor and remove the front end. Not a big deal but a necessary evil.

If your doing this type of repair it would be wise to have factory manual to assist with those (scratch your head) situations. www.agcopubs.com[/url If you going ... aid you over the rough edges. Good luck -kid

 

[vegaome]

Howdy pjbci,

That makes sense to me. I bought my tractor used and I do want to fix it up. I dont have a garage or engine stand, at least not yet. I may have to go this route. Thank you for sharing your story. I appreciate it.

v/r

Mike

 

[Leejohn]

You should make sure there is no oil film on the back side of the bearing that would give you about .002 under size. Might be a little hard to turn over.